Editorial

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Open AccessEditorial

Boron-Based (Nano-)Materials: Fundamentals and Applications

by Umit B. Demirci, Philippe Miele and Pascal G. Yot

Crystals 2016, 6(9), 118; https://doi.org/10.3390/cryst6090118 - 19 Sep 2016

Cited by 5 | Viewed by 5585

The boron (Z = 5) element is unique. Boron-based (nano-)materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-)materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes [...] Read more.

The boron (Z = 5) element is unique. Boron-based (nano-)materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-)materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes and carboranes, boronate anions/ligands, boron nitride (hexagonal structure), and elemental boron are considered. Importantly, large sections are dedicated to fundamentals, with a special focus on crystal structures. The application potentials are widely discussed on the basis of the materials’ physical and chemical properties. It stands out that crystalline boron-based (nano-)materials have many technological opportunities in fields such as energy storage, gas sorption (depollution), medicine, and optical and electronic devices. The present special issue is further evidence of the wealth of boron science, especially in terms of crystalline (nano-)materials. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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Research

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12231 KiB

Open AccessArticle

Hydrogen Desorption Properties of Bulk and Nanoconfined LiBH₄-NaAlH₄

by Payam Javadian, Drew A. Sheppard, Craig E. Buckley and Torben R. Jensen

Crystals 2016, 6(6), 70; https://doi.org/10.3390/cryst6060070 - 20 Jun 2016

Cited by 20 | Viewed by 5306

Abstract

Nanoconfinement of 2LiBH₄-NaAlH₄ into a mesoporous carbon aerogel scaffold with a pore size, BET surface area and total pore volume of D_max = 30 nm, S_BET = 689 m²/g and V_tot = 1.21 mL/g, respectively [...] Read more.

Nanoconfinement of 2LiBH₄-NaAlH₄ into a mesoporous carbon aerogel scaffold with a pore size, BET surface area and total pore volume of D_max = 30 nm, S_BET = 689 m²/g and V_tot = 1.21 mL/g, respectively is investigated. Nanoconfinement of 2LiBH₄-NaAlH₄ facilitates a reduction in the temperature of the hydrogen release by 132 °C, compared to that of bulk 2LiBH₄-NaAlH₄ and the onset of hydrogen release is below 100 °C. The reversible hydrogen storage capacity is also significantly improved for the nanoconfined sample, maintaining 83% of the initial hydrogen content after three cycles compared to 47% for that of the bulk sample. During nanoconfinement, LiBH₄ and NaAlH₄ reacts to form LiAlH₄ and NaBH₄ and the final dehydrogenation products, obtained at 481 °C are LiH, LiAl, AlB₂ and Al. After rehydrogenation of the nanoconfined sample at T = 400 °C and p(H₂) = 126 bar, amorphous NaBH₄ is recovered along with unreacted LiH, AlB₂ and Al and suggests that NaBH₄ is the main compound that can reversibly release and uptake hydrogen. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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1678 KiB

Open AccessArticle

Influence of Defects in Boron Nitride Nanotubes in the Adsorption of Molecules. Insights from B3LYP-D2* Periodic Simulations

by Oriol Matarín and Albert Rimola

Crystals 2016, 6(5), 63; https://doi.org/10.3390/cryst6050063 - 20 May 2016

Cited by 23 | Viewed by 5936

Abstract

The adsorption of H₂O, NH₃ and HCOOH as polar molecules and C₆H₆ and CH₄ as non-polar ones on a series of zig-zag (6,0) single-walled boron nitride nanotubes (BNNTs) both being defect-free (P_BNNT) and containing defects at [...] Read more.

The adsorption of H₂O, NH₃ and HCOOH as polar molecules and C₆H₆ and CH₄ as non-polar ones on a series of zig-zag (6,0) single-walled boron nitride nanotubes (BNNTs) both being defect-free (P_BNNT) and containing defects at the nanotube walls has been studied by means of B3LYP-D2* periodic calculations. We focused on defects derived from monovacancies of B (N-rich_BNNT) and N (B-rich_BNNT) atoms and also on Stone-Wales defects (SW_BNNT). The adsorption of polar molecules with defective BNNTs is generally based on dative interactions and H-bonding, and their adsorption energies strongly depend on the type of BNNT. N-rich_BNNT is the most reactive nanotube towards adsorption of polar molecules, as in all cases deprotonation of the polar molecules is spontaneously given upon adsorption. The strength in the adsorption energies is followed by B-rich_BNNT, SW_BNNT and P_BNNT. Adsorption of non-polar molecules is mainly dictated by dispersion interactions, and, accordingly, the adsorption energies are almost constant for a given molecule irrespective of the type of nanotube. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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1707 KiB

Open AccessArticle

In situ Synchrotron X-ray Thermodiffraction of Boranes

by Pascal G. Yot, Philippe Miele and Umit B. Demirci

Crystals 2016, 6(2), 16; https://doi.org/10.3390/cryst6020016 - 25 Jan 2016

Cited by 8 | Viewed by 5358

Abstract

Boranes of low molecular weight are crystalline materials that have been much investigated over the past decade in the field of chemical hydrogen storage. In the present work, six of them have been selected to be studied by in situ synchrotron X-ray thermodiffraction. [...] Read more.

Boranes of low molecular weight are crystalline materials that have been much investigated over the past decade in the field of chemical hydrogen storage. In the present work, six of them have been selected to be studied by in situ synchrotron X-ray thermodiffraction. The selected boranes are ammonia borane NH₃BH₃ (AB), hydrazine borane N₂H₄BH₃ (HB), hydrazine bisborane N₂H₄(BH₃)₂ (HBB), lithium LiN₂H₃BH₃ (LiHB) and sodium NaN₂H₃BH₃ (NaHB) hydrazinidoboranes, and sodium triborane NaB₃H₈ (STB). They are first investigated separately over a wide range of temperature (80–300 K), and subsequently compared. Differences in crystal structures, the existence of phase transition, evolutions of unit cell parameters and volumes, and variation of coefficients of thermal expansion can be observed. With respect to AB, HB and HBB, the differences are mainly explained in terms of molecule size, conformation and motion (degree of freedom) of the chemical groups (NH₃, N₂H₄, BH₃). With respect to LiHB, NaHB and STB, the differences are explained by a stabilization effect favored by the alkali cations via M···H interactions with four to five borane anions. The main results are presented and discussed herein. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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2341 KiB

Open AccessArticle

Influence of Boron on Initial Austenite Grain Size and Hot Deformation Behavior of Boron Microalloyed Steels

by Yong-liang Gao, Xiang-xin Xue and He Yang

Crystals 2015, 5(4), 592-607; https://doi.org/10.3390/cryst5040592 - 24 Nov 2015

Cited by 13 | Viewed by 5407

Abstract

The initial austenite grain size of boron microalloyed steel with three different amounts of boron (20, 40, and 60 ppm) was investigated under different heating temperatures (1150, 1100, and 1050 °C), and hot compression tests of samples in a wide range of temperature [...] Read more.

The initial austenite grain size of boron microalloyed steel with three different amounts of boron (20, 40, and 60 ppm) was investigated under different heating temperatures (1150, 1100, and 1050 °C), and hot compression tests of samples in a wide range of temperature (900–1100 °C) and strain rate (0.1–10 s⁻¹) were conducted. It was found that the initial austenite grain size increases with increasing temperature and boron content. The flow stress decreased with increasing boron content at lower strain rates. The flow stress constitutive equation of hot deformation was developed for the experimental steels; results showed that boron addition has the trend to reduce the hot deformation activation energy. The characteristic points of the flow curves were analyzed. Results revealed that the peak and critical stress decreased in response to an increase of boron content. The work-hardening behavior of both steels was investigated, and it was found that boron addition can decrease the work-hardening rate when strained at lower strain rates. On the contrary, peak and critical strains increased as boron content increased, indicating that boron has the ability to delay the onset of dynamic recrystallization. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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Review

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Open AccessReview

Mono- and Bimetalic Amidoboranes

by Rafał Owarzany, Piotr J. Leszczyński, Karol J. Fijalkowski and Wojciech Grochala

Crystals 2016, 6(8), 88; https://doi.org/10.3390/cryst6080088 - 05 Aug 2016

Cited by 35 | Viewed by 5821

Abstract

In this review, we present an overview on metal amidoboranes, which have recently been considered as hydrogen storage materials for fueling of the low temperature fuel cells. We focus on amidoborane salts containing only metal cations and amidoborate anions. During the last decades, [...] Read more.

In this review, we present an overview on metal amidoboranes, which have recently been considered as hydrogen storage materials for fueling of the low temperature fuel cells. We focus on amidoborane salts containing only metal cations and amidoborate anions. During the last decades, 19 new compounds from this group were described in the literature. We provide a summary of various physical and chemical properties of amidoborane compounds reported up to date. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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Silver and Copper Complexes with closo-Polyhedral Borane, Carborane and Metallacarborane Anions: Synthesis and X-ray Structure

by Varvara V. Avdeeva, Elena A. Malinina, Igor B. Sivaev, Vladimir I. Bregadze and Nikolai T. Kuznetsov

Crystals 2016, 6(5), 60; https://doi.org/10.3390/cryst6050060 - 20 May 2016

Cited by 69 | Viewed by 9091

Abstract

Synthesis and structure of silver and copper salts and complexes with polyhedral boron hydride anions, including closo-decaborate [B₁₀H₁₀]²⁻, closo-dodecaborate [B₁₂H₁₂]²⁻, 1-carba-closo- decaborate [1-CB₉H₁₀] [...] Read more.

Synthesis and structure of silver and copper salts and complexes with polyhedral boron hydride anions, including closo-decaborate [B₁₀H₁₀]²⁻, closo-dodecaborate [B₁₂H₁₂]²⁻, 1-carba-closo- decaborate [1-CB₉H₁₀]⁻, carba-closo-dodecaborate [CB₁₁H₁₂]⁻, and cobalt bis(dicarbollide) [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ anions and their derivatives, are reviewed. The complexes demonstrate a wide variety of structural types, relating to both the metal coordination environment and coordination modes of boron hydride anions. The latter can range from strong coordination via the polyhedron triangular face including formation of 3c-2e MHB bonds in the case of the [B₁₀H₁₀]²⁻ dianion, the structure of which contains two four-coordinated boron atoms, to very weak M…H interactions with the hydride atoms in the case of bulky [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ monoanion. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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How to Increase the h-BN Crystallinity of Microfilms and Self-Standing Nanosheets: A Review of the Different Strategies Using the PDCs Route

by Sheng Yuan, Catherine Journet, Sébastien Linas, Vincent Garnier, Philippe Steyer, Stéphane Benayoun, Arnaud Brioude and Bérangère Toury

Crystals 2016, 6(5), 55; https://doi.org/10.3390/cryst6050055 - 13 May 2016

Cited by 20 | Viewed by 9613

Abstract

Hexagonal boron nitride (h-BN) is a well-known material whose use is almost restricted to lubricating applications in domains ranging from metallurgy to cosmetics. Howover, h-BN displays many other interesting properties, opening new perspectives for other engineering applications, such as as a solid lubricant [...] Read more.

Hexagonal boron nitride (h-BN) is a well-known material whose use is almost restricted to lubricating applications in domains ranging from metallurgy to cosmetics. Howover, h-BN displays many other interesting properties, opening new perspectives for other engineering applications, such as as a solid lubricant in aeronautics, as the perfect substrate to graphene for electronic devices, etc. However, all these promising developments require tailored h-BN shapes displaying a high level of crystallization, ensuring its properties for the long term. Here, we developed three strategies, all associated with the Polymer Derived Ceramics (PDCs) route, to prepare highly crystallized supported thick coatings and self-standing nanosheets. The first strategy concerns the innovative implementation of a Rapid Thermal Annealing to prepare micrometric h-BN coatings on thermal sensitive substrates. Compared to conventional treatment the crystallization of h-BN has successfully lowered to about 300 °C. The second strategy consists of an additivation of the used polymer precursor. Effect of lithium nitride as a crystallization promoter was investigated lowering the onset crystallization temperature from 1400 °C (traditionally) to 1000 °C. This novel synthetic route allows preparing self-standing highly crystallized h-BN nanolayers. Finally, the third strategy is based on a unique combination of the PDCs route with Spark Plasma Sintering to profit of both approaches. This original method leads to large and well-crystallized flakes available for a subsequent exfoliation. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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8083 KiB

Open AccessReview

N,O-Type Carborane-Based Materials

by José Giner Planas, Francesc Teixidor and Clara Viñas

Crystals 2016, 6(5), 50; https://doi.org/10.3390/cryst6050050 - 04 May 2016

Cited by 19 | Viewed by 7601

Abstract

This review summarizes the synthesis and coordination chemistry of a series of carboranyl ligands containing N,O donors. Such carborane-based ligands are scarcely reported in the literature when compared to other heteroatom-containing donors. The synthetic routes for metal complexes of these N,O-type carborane ligands [...] Read more.

This review summarizes the synthesis and coordination chemistry of a series of carboranyl ligands containing N,O donors. Such carborane-based ligands are scarcely reported in the literature when compared to other heteroatom-containing donors. The synthetic routes for metal complexes of these N,O-type carborane ligands are summarized and the properties of such complexes are described in detail. Particular attention is paid to the effect that the incorporation of carboranes has into the coordination chemistry of the otherwise carbon-based ligands and the properties of such materials. The reported complexes show a variety of properties such as those used in magnetic, chiroptical, nonlinear optical, catalytic and biomedical applications. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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3990 KiB

Open AccessReview

Coordination Networks Based on Boronate and Benzoxaborolate Ligands

by Saad Sene, Marie Alix Pizzoccaro, Joris Vezzani, Marc Reinholdt, Philippe Gaveau, Dorothée Berthomieu, Sylvie Bégu, Christel Gervais, Christian Bonhomme, Guillaume Renaudin, Adel Mesbah, Arie Van der Lee, Mark E. Smith and Danielle Laurencin

Crystals 2016, 6(5), 48; https://doi.org/10.3390/cryst6050048 - 02 May 2016

Cited by 9 | Viewed by 7650

Abstract

Despite the extensive range of investigations on boronic acids (R-B(OH)₂), some aspects of their reactivity still need to be explored. This is the case for the coordination chemistry of boronate anions (R-B(OH)₃⁻), which has only recently been started [...] Read more.

Despite the extensive range of investigations on boronic acids (R-B(OH)₂), some aspects of their reactivity still need to be explored. This is the case for the coordination chemistry of boronate anions (R-B(OH)₃⁻), which has only recently been started to be studied. The purpose of this review is to summarize some of the key features of boronate ligands (and of their cyclic derivatives, benzoxaborolates) in materials: (i) coordination properties; (ii) spectroscopic signatures; and (iii) emerging applications. Full article

(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)

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